1. Field of the Invention
The present invention relates to a lamp used primarily as a lighting device in a vehicle, such as a headlamp, or a fog lamp. More particularly, the present invention relates to a so-called xe2x80x9cprojector typexe2x80x9d lamp which uses a reflection mirror whose shape is based on an ellipse, which is a curve having two focal points, i.e., the first focal point and the second focal point, in which the profile of light from a light source converging at the second focal point is projected through a projection lens toward the illuminating direction so as to obtain a luminous intensity distribution property.
2. Detailed Description of the Prior Art
FIG. 15 illustrates an exemplary configuration of a lamp 90 which is a conventional projector type lamp. The lamp 90 includes a light source 91, an elliptical reflector 92 (a spheroid reflector, a composite ellipse reflector, or an elliptical free form curved surface) whose first focal point is at the light source 91, an aspheric lens 93, and a shade 94 which is provided as necessary. The image of the light source converging at the second focal point is enlarged and projected through the aspheric lens 93 so as to obtain illumination light.
Where a luminous intensity distribution property with no upward light such as, for example, a low beam luminous intensity distribution (i.e., a luminous intensity distribution with substantially no light beam directed in an upward direction, which is desired particularly when there is another car coming from the opposite direction) is required, the shade 94 may be used to block the lower half of the light beam converging at the second focal point from the light source 91, whereby light projected from the aspheric lens 93 contains no upward light, thus obtaining a desired luminous intensity distribution property.
However, in the above-described conventional projector type lamp 90, the elliptical reflector 92 and the aspheric lens 93 are arranged optically in series, thereby increasing the front-to-back dimension of the lamp 90. Therefore, where the lamp 90 is to be installed in a vehicle, or the like, a relatively large space is required in the vehicle, thereby creating difficulties in installation. Moreover, in the projector type lamp 90, the diameter of the aspheric lens 93 is small and thus the area through which light is emitted is not large, thereby deteriorating the visibility thereof for cars coming from the opposite direction or for pedestrians. Furthermore, where the low beam luminous intensity distribution is provided, about one half of the total amount of light available is blocked by the shade 94, thereby lowering the efficiency of use of the light beam generated from the light source 91.
The present invention provides the following multi-lens projector lamp as practical means for solving the above-described conventional problems. Such a multi-lens projector lamp is a multi-lens projector lamp, which is a lighting device using a single light source, wherein four or more aspheric lenses whose optical axes are oriented in the same direction are arranged at any positions shifted in an upper, lower, left, right, forward or rear direction from a lamp center, the multi-lens projector lamp comprising a reflector provided in a rear peripheral region of each of the aspheric lenses along the optical axis thereof for generating reflected light to be incident upon the aspheric lens, the reflector being one selected from the group consisting of:
{circle around (1)} a reflector formed of a combination of strip-shaped spheroid segments or an ellipse-based free form curved surface, having a first focal point in the vicinity of the light source and an infinite number of second focal points in a range which is defined from a focal point of the associated aspheric lens to a tip of the lens and within a diameter of the lens;
{circle around (2)} a reflector formed of a combination of strip-shaped spheroid segments or an ellipse-based free form curved surface, having a first focal point in the vicinity of the light source and second focal points which are distributed to positions along a focal point line within a horizontal divergent angle of the focal point line, the focal point line extending in the horizontal direction at a level of a center of the associated aspheric lens and being curved toward the lens side from a focal point inherent to the aspheric lens;
{circle around (3)} a reflector formed of a combination of strip-shaped spheroid segments or an ellipse-based free form curved surface, wherein the reflector is divided into an upper section and a lower section at a center of the associated aspheric lens, the upper reflector section having a first focal point at a front end of the light source, the lower reflector section having a first focal point at a rear end of the light source, and wherein the reflector has second focal points which are distributed to positions along a focal point line within a horizontal divergent angle of the focal point line, the focal point line extending in the horizontal direction at a level of a center of the associated aspheric lens and being curved toward the lens side from a focal point inherent to the aspheric lens; and
{circle around (4)} a reflector formed of a combination of strip-shaped spheroid segments or an ellipse-based free form curved surface, wherein the reflector is divided into a plurality of regions in upper, lower, left, right, and diagonal directions taking into consideration a position of the associated aspheric lens, each of the reflector regions having a first focal point in the vicinity of the light source and second focal points, wherein the second focal points are, for the horizontal direction, distributed to positions along a focal point line within a horizontal divergent angle of the focal point line, the focal point line extending in the horizontal direction at a level of a center of the associated aspheric lens and being curved toward the lens side from a focal point inherent to the aspheric lens, and the second focal points are, for the vertical direction, shifted upwardly to any positions, wherein:
reflectors of the reflectors include: single reflection sections, respectively corresponding to 3 to 5 lenses at or near the lamp center at which the light source is located, for providing a single reflection whereby the reflected light is incident upon the associated aspheric lens; and one or more double reflection section, respectively corresponding to one or more lenses located on either side or both sides of the 3 to 5 lenses, for providing a double reflection whereby the reflected light is incident upon the associated aspheric lens, each of the one or more double reflection section functioning as a combination of two reflectors, and wherein each of the one or more double reflection section is formed of the combination of strip-shaped spheroid segments, or the combination of the ellipse-based free form curved surface and a planar or quadric surface.
By employing the configurations as described above, the multi-lens projector lamp of the present invention can provide a novel appearance over conventional projector lamps. The present invention not only improves the appearance of the lamp alone, but also provides a novel appearance over the prior art when the lamp is installed in a vehicle, thereby improving the appearance of the vehicle.
By employing the configurations as described above, it is possible to significantly increase the area through which light is emitted while using a single light source, thereby improving the visibility for cars coming from the opposite direction and thus providing an excellent effect in ensuring safety. These effects of the present invention can be obtained only with a single light source as described above. Therefore, the present invention also has an advantage in that the present invention can be carried out without substantially increasing the production cost. Moreover, since the light from a single light source is distributed among a plurality of aspheric lenses, the amount of heat per one aspheric lens is reduced, thereby enabling one to make the aspheric lens with a resin, which has been impossible in the prior art. Also by this advantage, the present invention provides an excellent effect of reducing the production cost.
Furthermore, the reflector of the present invention can be configured in the form of an open ellipse, thereby enabling one to make a lamp with a reduced average front-to-back dimension. Thus, the present invention facilitates the installation of the lamp in a vehicle by eliminating the need to provide a large recess in the vehicle for the installation. Moreover, all the aspheric lenses are appropriately positioned with respect to the respective reflector sections, thereby improving the efficiency of use of light and thus obtaining a bright lamp. Therefore, the present invention also provides an excellent effect of improving the performance of the lamps of this type.